1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.
In this specification, a semiconductor device means all types of devices which can function by utilizing semiconductor characteristics, and an electro-optical device, a semiconductor circuit, and an electronic device are all semiconductor devices.
2. Description of the Related Art
A technique by which a transistor is formed using a semiconductor thin film formed over a substrate having an insulating surface has been attracting attention. Such a transistor is applied to a wide range of electronic devices such as an integrated circuit (IC) and an image display device (also simply referred to as a display device). A silicon-based semiconductor material is widely known as a material for a semiconductor thin film applicable to a transistor. As another material, an oxide semiconductor has been attracting attention.
For example, a transistor formed using a semiconductor layer which includes an amorphous oxide containing indium (In), gallium (Ga), and zinc (Zn) (IGZO-based amorphous oxide) is disclosed (see Patent Document 1).